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Date: Fri, 13 Jun 2025 07:54:33 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Zhang Yi <yi.zhang@huaweicloud.com>, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org, linux-block@vger.kernel.org,
	dm-devel@lists.linux.dev, linux-nvme@lists.infradead.org,
	linux-scsi@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-kernel@vger.kernel.org, tytso@mit.edu,
	john.g.garry@oracle.com, bmarzins@redhat.com, chaitanyak@nvidia.com,
	shinichiro.kawasaki@wdc.com, brauner@kernel.org,
	martin.petersen@oracle.com, yi.zhang@huawei.com,
	chengzhihao1@huawei.com, yukuai3@huawei.com, yangerkun@huawei.com
Subject: Re: [PATCH 01/10] block: introduce BLK_FEAT_WRITE_ZEROES_UNMAP to
 queue limits features
Message-ID: <20250613145433.GF6134@frogsfrogsfrogs>
References: <20250604020850.1304633-1-yi.zhang@huaweicloud.com>
 <20250604020850.1304633-2-yi.zhang@huaweicloud.com>
 <20250611060900.GA4613@lst.de>
 <343f7f06-9bf6-442f-8e77-0a774203ec3f@huaweicloud.com>
 <20250612044744.GA12828@lst.de>
 <41c21e20-5439-4157-ad73-6f133df42d28@huaweicloud.com>
 <20250612150347.GK6138@frogsfrogsfrogs>
 <3569a77f-1f38-4764-b1e3-d0075775c7bb@huaweicloud.com>
 <20250613055630.GA9119@lst.de>
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In-Reply-To: <20250613055630.GA9119@lst.de>

On Fri, Jun 13, 2025 at 07:56:30AM +0200, Christoph Hellwig wrote:
> On Fri, Jun 13, 2025 at 11:15:41AM +0800, Zhang Yi wrote:
> > Yeah, this solution looks good to me. However, we currently have only
> > two selections (none and unmap). What if we keep it as is and simply
> > hide this interface if BLK_FEAT_WRITE_ZEROES_UNMAP is not set, making
> > it visible only when the device supports this feature? Something like
> > below:
> 
> I really hate having all kinds of different interfaces for configurations.

I really hate the open-coded string parsing nonsense that is sysfs. ;)

> Maybe we should redo this similar to the other hardware/software interfaces
> and have a hw_ limit that is exposed by the driver and re-only in
> sysfs, and then the user configurable one without _hw.  Setting it to
> zero disables the feature.

Yeah, that fits the /sys/block/foo/queue model better.

--D